Fog inhibitor for photographic emulsions



general or chemical fog.

Patented Mar. 9, 1943 R PHOTOGC SION S George E. Fallesen and John A. Leer-makers, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester,

New Jersey N. Y., a. corporation of NoDrawing. Application A 9, 1941,

- Serial No. 406,172

Claims.

This invention relates to fog inhibitors for photographic emulsions and to photographic emulsions containing them.

It is known that photographic emulsions particularly ultra-sensitive emulsions, or those containing color sensitizers exhibit a tendency to form a deposit of silver in the emulsion. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic fog is of two types, local and general. Local iog is formed by exposure of the film or plate at undesired points, as by a light leak in the camera. Genera1 fog or, as it is sometimes known, chemical fog, is formed in a number of ways. It may be caused by the conditions under which the film or plate isstored, such as conditions of high temperature or unusually long time of storage. The nature of the emulsion may also produce chemical fog, as well as the conditions of development of the emulsion, as by development for protracted periods of time or at temperatures above normal. Highly sensitive emulsions are more likely to fog than those of lower sensitivity. We are concerned primarily with The primary objector the present invention is to provide anti-fogging or fog inhibiting agents for ultra-sensitive photographic emulsions and to thereby increase the stability of the emulsions. A further object is to provide anti-fogging agents which do not markedly lower th sensitivity of the emulsion.

These objects are accomplished vby incorporating in the emulsion an acetylamino phenol or diacetylamino phenol. v

These compounds are incorporated in a fast. negative emulsion particularly a silver halide emulsion which contains optical sensitizing dyes. The emulsion used may be one which is intended to be used directly after emulsification or one which is subjected to ripening.

The following examples'illustrate compounds which we have found suitable for inhibiting fog in photographic emulsions.

nncocm a on Acetyl-m-sminophenol onto DEN-Q0151 V Acetyl-p-aminophenol coon;

' N\ coon! We have found that in the case of the monoacetylaminophenols the anti-foggant action is least in the ortho compounds, greater in the para compounds and greatest in the meta compounds.

Y This is also true in general of the diacetylamino as'phenols. The eflect of the compounds on photographic speed was also found to be related to the position of the substituents and to the number of acetyl groups in the compounds. The desensitizing efiect was observed to-be greater with 40 the monoacetylamino phenols than with the diacetylamino phenols.

' tization caused by the diacetylamino phenols was found to be practically negligible and under most conditions these compounds seem to be very useful antiioggants. Y

The antifoggant action was determined by incubation oi! the emulsions under simulated tropical conditions for two weeksand also by incuba- :tion for a similar length or time in dry heat at F. The results or the latter tests are tabu- The amount of desensilated here for comparison with the initial fog in the emulsions with and without the antifoggants.

and. Isl-ray emulsions. If used with sensitizing dyes they may be added to the emulsion before or sitized emulsion and Pan. sens. means a panchromatically sensitized emulsion. The amount of fog was determined by reading the density at the toe of the curve after exposure and development of the emulsions, in the usual manner.

The amount of the fog inhibiting agents used in the emulsion will depend upon the composition of the agent and uponthe type of emulsion. In general, the amount of fog inhibiting agent used will vary from 1 gram to 10 grams per 1000 cc. of wet emulsion. It will be understood that more or less than this amount may be used. Generally, however, if a greater amount is used in the emulsion either no increased fog inhibiting efiect is obtained or there is a decrease in the sensitivity of the emulsion. These compounds may be incorporated by mixing them with any suitable sol- 5 vent which is inert with respect to the emulsion such. as water, methyl alcohol, ethyl alcohol, acetone, and others.

The fog inhibiting agents which we have described may be used in various kinds of photo graphic emulsions. In addition to being useful in ordinary non-sensitized emulsions, they may be used also in orthochromatic, panchromatic 14-day 120 F. incubalnitlal fog on fog N me of compound Emulsion Emulsion Emulsion Emulsion with without with without compound compoun'd compound compound Acetyl m-amino-phenol, 8.3 grams per liter Unsens Acetyl p-amino-phenol, 8.33 grams per liter Diaoetyl-o-amino-phenol, 4.16 grams per liter ,Diacctyl m-amino-pheno], 4.16 grams per liter Diacetyl p-amino-phenol, 4.16 grams per liler.. Gem

In the above table Unsens. means an unsenafter the dyes are added. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, and mixtures of these. The dispersing agent may be gelatin or other colloid such as'collodion, albumen, cellulose organic derivatives or synthetic resins.

It is to be understood that we contemplate as included within our invention all modifications and equivalents falling within the scope of the appended claims.

We claim:

1. A gelatino-silver halide emulsion containing as an antifoggant a diacetylamino phenol.

2. A gelatino-silver halide emulsion containing a diacetylaminophenol in fog inhibiting amounts.

3. A gelatino-silver halide emulsion containing as an antifoggant diacetyl-m-aminophenol.

4. A gelatino-silver halide emulsion containing as an anti-foggant diacetyl-p-aminophenol.

5. A gelatino-silver bromide emulsion containing as an antifoggant approximately 4 grams per liter of diacetyl-m-amino'phenol.

GEORGE E. FALLESEN. JOHN A. LEERMAKERS. 

